1. Field of the invention
The invention relates to an image sensor, and in particular to a miniaturized image sensor that may be manufactured easily.
2. Description of the Related Art
Referring to FIG. 1, a conventional image sensor includes a substrate 10, a frame layer 18, a photosensitive chip 26, a plurality of wires 28 and a transparent layer 34. The substrate 10 has a first surface 12 formed with signal input terminals 15 and a second surface 14 formed with signal output terminals 16 which are electrically connected to a printed circuit board (not shown). The frame layer 18 has an upper surface 20 and a lower surface 22, which is bonded to the first surface 12 of the substrate 10 to form a cavity 24 together with the substrate 10. The photosensitive chip 26 is arranged within the cavity 24 defined by the substrate 10 and the frame layer 18 and is mounted to the first surface 12 of the substrate 10. Each of the wires 28 has a first terminal 30 electrically connected to the photosensitive chip 26 and a second terminal 32 electrically connected to a corresponding signal input terminal 15 of the substrate 10. The transparent layer 34 is disposed on the upper surface 20 of the frame layer 18.
When the photosensitive chip 26 is made larger, the gap between the chip 26 and the frame layer 18 is shortened. So, it is difficult to bond and electrically connect the wires 28 to the signal input terminals 15 of the substrate 10 owing to the shortened gap. It is possible to enlarge the substrate 10. However, enlarging the substrate 10 cannot meet the miniaturized requirement.
Furthermore, a substrate 10 has to be prepared in advance, traces have to be formed on the substrate 10, and a frame layer 18 has to be adhered onto the substrate 10. Consequently, the manufacturing processes are complicated and the material costs are relatively high.
In view of the above-mentioned problems, it is therefore an object of the invention to provide a miniaturized image sensor that may be made conveniently.
An object of the invention is to provide a miniaturized image sensor that is easy to be manufactured with a high yield.
Another object of the invention is to provide a miniaturized image sensor that may be manufactured with lower costs.
Still another object of the invention is to provide a miniaturized image sensor having a relatively small height.
To achieve the above-mentioned objects, an image sensor of the invention includes a substrate, a frame layer, a photosensitive chip and a transparent layer. The substrate is composed of plural spaced metal sheets. Each metal sheet includes a first board, a second board and a third board connecting the first board to the second board. The first and second boards are located at different heights. The frame layer has an upper surface and a lower surface. The frame layer covers and seals the metal sheets while exposes bottom surfaces of the second boards of the metal sheets. The frame layer is formed with a chamber on the lower surface thereof. Bottom surfaces of the first boards of the metal sheets are exposed through the chamber, and a transparent region communicating with the chamber is formed on the upper surface of the frame layer. The photosensitive chip is formed with a plurality of bonding pads and disposed within the chamber. The bonding pads respectively contact the bottom surfaces of the first boards of the substrate in a flip-chip manner for signal transmission from the photosensitive chip, which receives optical signals passing through the transparent region of the frame layer. The transparent layer is mounted on the upper surface of the frame layer to cover the transparent region of the frame layer.
Accordingly, the overall height of the package may be reduced because the photosensitive chip is disposed within the chamber and is electrically connected to the substrate in a flip-chip manner. Furthermore, the manufacturing processes are more convenient because the metal sheets and the frame layer are formed integrally and no traces have to be formed on the substrate.